A conventional physical keyboard is bulky and difficult to clean, and therefore there are virtual keyboards obtained by projecting a keyboard on a flat surface, as an alternative. However, users have a hard time adapting to such projected virtual keyboards because they are not user-friendly, and since types and forms are limited, users should adapt to the shape of the keyboard. In addition, these keyboards require expensive hardware resources and an infrared receiver for recognizing a keyboard input of a user in order to form a virtual keyboard.
In addition, in the case of the virtual keyboard applied to a tablet PC, a smartphone, etc., there is a problem that the virtual keyboard covers nearly half of the screen. In addition, when 2-byte characters, special characters, numbers, and the like should be alternately input, keys on the virtual keyboard are also displayed alternately on the screen, and therefore there is a problem that the key input is inconvenient.